Sea Pens (cnidarians belonging to the order Pennatulacea): Sea pens are grouped with the octocorals (“soft corals”). They were named after their feather-like appearance reminiscent of antique quill pens. Sea pens may rise up to 6.6 ft in some species and are sometimes brightly colored. Rarely found above depths of 30 ft, sea pens prefer deeper waters where turbulence is less likely to uproot them.